Protractor



G. SALOT. u Protractor.

No. 227,844. Patented May l18, 1880.

lllllllnllllllllll HllllllllllllHlll lll e IIIHIIII HIHIIIHIIIIIII]|||||||||II||I|IHI lll NFETERS. FHOTG-IJTHDGRAPHER. WASHINGTON. D4 CVAUNITED STAT-ns ATENT Ormea,

GEORGE SALOT, OF DUBUQUE, IOWA.

PROTRACTOR.

SPECIFICATION forming part of Letters `Patent No. 227,844, dated May 18,1880.

Application iilcd Februaty, 1880.

To all 'whom it may concern: v

Be it known that I, GEORGE SALOT, of Dubuque, in the county of Dubuqueand State of "Iowa, have invented a new and useful Improvement inProtractors; and I do hereby declare that the following is a full andexact description of the same, reference being had to the accompanyingdrawings, and to the letters of reference marked thereon.

This invention relates to a class of instruments used by draftsmen, moreparticularly for plotting in map-work. y

It consists ofa circular protractor, to which is attached on the sideot' the chord, at right angles to it, a graduated rule of any convenientlength and width. This protractor with its rule is pivoted upon asegmental standard or base-line support.

It also consists in the various operative combinations of the severalparts, all as more fully hereinafter described and explained.

In order that those skilled in the art may know how to make and use thisinstrument, I proceed to describe the same, having reference to theaccompanying drawings, in which- Figure lis a plan view of the same,Fig. 2, a central vertical section through the lower part of the same,and Figs. 3 and 4 details of the pivotal screw and thumb-screw connectedwith the same.

Like letters denote corresponding parts in each figure. v l

In the drawings, Arepresents the rule, and B the protractor, each madeof suitable metal, preferably struck out of sheet metal in Ione piece,the rule being attached at right angles to the center of the outside ofthe chord of the protractor, which is semicircular in outline.

The protractoris graduated on its curved surface in the followingmanner: The degrees on the outer line are numbered from zero at thecenter to ninety degrees at each corner. The

second row of degrees is numbered from right to left, commencing withzero at the right and running to one hundred and eighty degrees at theleft-hand corner. The third row of degrecs is numbered from left toright, ruiming belong. The chord ofthe protractoris also graduated oneach side ot' thedouble-edged :rule in a similar way, for the purpose ofdrawin g parallel lines, and also lines running in any direction.

' The segmental standard or base-line support C may be a casting of anysuitable metal, preferably of segmental form, with a base., a, of a truestrai gh t line, tlan ged on one side, as at b, so as to raise theprotractor when in use above the paper on which it rests. The protractorand rule are pivoted to this segmental standard at the point where therule joins the chord of the segmentalstandard, and for convenience and`security in use the curveof the protractor eX- tends down as far as theflange b, and the base of the standard is cut away a little on its frontfor more convenient reading of the tigures upon the protractor.

A screw, D, having the part 0 next to its head' made square, passesloosely through the rule, then through a square hole, d, in thesegmental standard, to which the square part of the screw ts closely.

A thumb-screw, E, serves, when turned tightly in one direction, to holdthe protractor and rule and segmental standard tightly together. Whenturned in the other direction it allows the protractor and ruleto bemoved in veither direction, as the square portion of the screw does notallow it to turn in the segmental standard, while the size of thescrew-opening in the protractor and rule permits a freedom of movementof them. A stud or pin, e, enables the rule to be moved moreconveniently by the linger. rule A is graduated in the usual way ofdraftsmens scales.

The following is the manner of operation of this device: The paper onwhich any drawing is to be made being tacked in the ordinary manner tothe drawing-board, and an ordinary T-square placed upon the same, thebase of the segmental standard is brought closely against the side ofthesquare, the instrument lying flat upon the paper. A point is designatedfrom which to start operations. The protractor is then turned until thedesired degrec-say ten degrees east-exactly touches a line, called, forconvenience, F, which is the center of the rule and of the protractor,run! ning through zero in its outer line of figures,

It is remarked that the IOO and a central mark designated upon the baseof the segmental standard, and then the screw l is tightened so th atthe protractor will not turn.

Then the T-square is moved, with the instrument resting upon it, untilone side of the rule just touches the commencing-point. The requireddistance is then drawn along the edge of the rule in the direction or'thedegree required-as, for instance, one inch. Ii', then, it is desiredto go ten degrees west-one inch-the protractor is turned until tendegrees west just touches thcline F, and the T-square with theinstrument is moved until the edge of the rule just touches the edge ofthe former line, and the one inch is marked along the edge of the rulein the direction indicated-namely, ten degrees west-and this process iscontinued until the plot is completed.

It' parallel lines are to be drawn at any angle the protractoris turneduntilthe desired degree touches the line F, and then one of theparallels is drawn along` the edge of the rule, and lthe distance thelines are to be apart is measured off from the graduated chord, and theinstrument moved from left to right or from right to left, as the casemay be, the required distance, and the other parallel is'drawn alongtheside of the rule, the rule in that case and the protractor remaining inthe same angle.

Among the advantages connected with this device are the following: Itdoes away with all dividers, and for plotting nothing more is requiredbut this instrument, a pencil, and a T- square or parallel rulers, andthe instrument need never be raised from the paper. The work 3 5 ofplotting' can therefore be done with much greater rapidity than with theordinaryT instruments. l

Having thus described my invention, what I claim as new therein is asfollows:

l. The combination, inaplotting-instrumcnt, of the segment-al standard Cand protractor B, constructed and arranged substantially as described,and for the purpose set forth.

2. The combination of the segmental stand- 45 ard C, protractor B, andrule A, substantially as and for the purposes set forth.

3. In a plotting-instrument, the combination, with the rule A andprotractor B, of the segmental standard C, screw D, and thumb- 5o screwE, all constructed and arranged to operate substantially as describedand shown.

4. The screw D, constructed and arranged substantially as described.

This specification signed and witnessed this 55 `30th day of January,1880.

GEORGE SALOT. Vitnesscs: i

G. L. TORBERT, MONROE M. GABY.

